1. Field of the Invention
The present invention relates to an art of providing a motor.
2. Description of Related Art
Motors are widely used in various fields. As one form of the motors, there is a motor having a claw-type magnetic pole. For example, JP-A-2001-161054 and JP-A-2003-513599 disclose the structure thereof.
First, in JP-A-2001-161054, a stator for one phase of the motor is composed of a circular coil through which current passes, a pair of claw-type magnetic poles, and a magnetic body surrounding the coil to form a magnetic path together with the claw-type magnetic poles.
In the case of a three-phase motor, its stator can be formed by using three sets of the above described stators. When three-phase voltage is applied to the three sets of the stators, rotational torque is generated in a rotor to which a permanent magnet is fixed, so that the rotor is rotated. This motor is characterized in that there is not a coil end and thus reduction in size of the motor can be achieved, as compared with a conventional motor.
Further, JP-A-2003-513599 discloses that a three-phase motor is constructed, for example, by providing one set of stators with coils for three phases so that the motor has a thin structure, rather than by superposing three sets of the stators each for one phase on one another as disclosed in JP-A-2001-161054.
Incidentally, in a reference example shown in FIG. 17, a magnetic path for one phase of a stator is formed by combining stator cores 81 and 83 having claw-type teeth so as to be opposed to each other. A coil 82 is build into an inner space formed by combining the stator cores 81 and 83 to constitute a one-phase stator. As shown in FIG. 11, similar one-phase stators 85 and 86 are superposed on this one-phase stator 80 to form a three-phase stator, and a rotor is combined therewith to constitute a three-phase motor 100. A method of integrally molding a stator core having such claw-type magnetic poles out of a magnetic powder material using a pressing machine is characterized in that a three-dimensional shape can be easily molded.
The motor in which the stator is configured to have the claw-type magnetic poles by molding those out of such a magnetic powder material has the following problem. In order to obtain desired performance by integrally molding the stator core out of the magnetic powder material, it is necessary to make the mass density of the stator core high. For this purpose, it is required to use a pressing machine with large compression force for the integral molding. Particularly, there is a limit in integrally molding a large output motor in view of the performance of the pressing machine.
Thus, in order to construct the large output motor using the magnetic powder material, it is necessary to integrally mold split cores into which the stator core is split, and thereafter use the plurality of split cores to assemble the stator. Since assembling accuracy of this stator influences the motor characteristics, it is a problem to enhance the assembling accuracy of the stator core. Further, also in the case of forming the stator cores for one phase by opposing the two stator cores to each other, it becomes a problem to enhance the assembling accuracy.